Since I could not get the video to load (waited several minutes), difficult to make any informed comments. A 5 - 6 inch daily water loss in a pond of any size is a major leak. Normally they occur somewhere around the waterfall and/or stream (if the installation has a stream). This amount of water would most certainly create a very wet area in the immediate vicinity of the leak if the leak is a result of water escaping OVER the edge of the liner. If, however, it is a hole or tear in the pond basin liner itself, it may be more difficult to isolate.
Have you turned off the water flow in an attempt to isolate the location of this leak? If you still experience water loss with the pump OFF, then the leak is in the pond proper. If not, then it is likely in the waterfall/stream. I have, however, seen leaks occur where plumbing unions were not securely glued.
"Everybody is ignorant, only on different subjects." - Will Rogers